Category Archives: DDW1

This is, I believe, the fourth trial of doing yeast growth time points. I setup the starter cultures and made some new YPD broth and here is how I did it:

I still had some YPD from the last time I made broth, so I used that for the starter cultures.

10ml of each type of YPD (DI, DDW, and D2O) in test tubes

Inoculated a single colony from agar media into each sample

Mix, cover, and incubate at 30C at 150RPM in shaker.

To make YPD broth:

Measure appropriate amount of YPD powder for each sample (5g for DI and DDW, 4.6g for D2O)

Measure out water (100ml of DDW and DI, 92ml of D2O)

Stir in beaker

Use syringe and filters to filter large particles and possible microbes in water/broth and syringe into closeable bottles.

Place in fridge for storage.

Notes:

There was a bunch of mold in some samples of the yeast colonies, so I threw those out in biowaste. In some other samples, the colonies were overgrown so I also put those in biowaste. I started another agar media colony (just streak a colony onto a ypd agar plate, pre-purchased) to replenish my stash.

I used only 92ml of D2O because that is all there was in the bottle. Since I’m using 50g/L ypd powder that means I need 4.6g of powder for my liquid media. Hence the numbers provided above.

This experiment went much better and more predictably. Yeast (unlike E. coli) is more sensitive to deuterium content and grows accordingly. Interestingly (in this experiment) the DDW sample exhibited more growth. I’ll have to experiment on this a bit more.

It should be noted that while it appears that pure D2O grows much slower than the rest (cause it does), I also started with a much lower amount of cells. The cells did not grow well in the starter culture, and they didn’t grow well here either. See the data (or the live results) for starting absorbance readings.

I don’t think this is a reliable data set. Several of the samples actually read a lower absorbance after the first hour than they initially do. And then they all dip again at hour 4.

I noticed a considerable amount of cell settling after hour 3 on the bottom of each test tube. I mixed prior to reading the absorbance values, but this is likely to skew the results. Next trial I will have to mix before reading every hour.

The data between DI, 30%, 60%, and 99% D2O look consistent with Tuesday’s results, but it scares me that the DDW and 90% D2O are completely out of whack.

Yesterday I set up starter cultures for this experiment using D2O, DDW, and DI water as the basis for the liquid media. Today I’m running the time trial experiment again, but this time with a bit more of a spectrum in water amounts. Here is the setup:

It should be noted that the 99% D2O starter culture was almost completely translucent. By this I mean it looked like there was no growth in the sample at all. Results that I’ll post later (when the experiment is complete) will show that this is indeed true, with an absorbance of 0.521 (compared to ~2.1 in both DI and DDW starter cultures, 4x the cell growth!).

I’ll be taking growth readings every hour via the nanodrop in micro cuvettes (til about hour 4) and then switching over to semi-micro cuvettes (because I’ll run out of micro cuvettes).